List of files installed and locations?

I posted the problem I am having in the mac opera section, however this was probably the more appropriate location.

I am having problems after uninstalling and re installing opera developer, where it still remembers bookmarks that were accidentally synced on install. I do not want any bookmarks brought over from firefox. However after re installing and making sure sync was un checked they still show up when I begin to type a url. They are not in the bookmarks folder. I would like to be able to do a clean install, and imagine that somewhere there are files that remained after the uninstall.

I am using mac os 10.10.5

Does anyone know the name and where those files are located? That way I can start without having the bookmarks showing up in Opera.